JP2003042723A - Light-intensity measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-accuracy film-thickness measuring apparatus. SOLUTION: The light-intensity measuring apparatus is provided with a light source 1, a first condensing optical system 2 which condenses light from the light source on a sample, a second condensing optical system 7 which condenses reflected light from the sample, a light detection part 8 which detects the reflected light from the sample via the optical system 7, and a measuring means 9 which measures a change in the light intensity of the reflected light detected by the part 8. The measuring apparatus is provided with either a means by which the sample is arranged in the defocus position of the optical system 2, or a means by which the light receiving face of the part 8 is arranged in the defocus position of the optical system 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film thickness measuring device for a thin film formed on a substrate such as a semiconductor substrate or a glass substrate for a liquid crystal panel, and film formation in a manufacturing process of a glass substrate for a semiconductor substrate or a liquid crystal panel. The present invention relates to a light intensity measuring device such as an end point detecting device for etching and flattening processes, and a real-time film thickness monitor.

[0002]

2. Description of the Related Art For example, in the process of manufacturing a semiconductor device, to measure the thickness of a thin film formed on a substrate,
Generally, an optical method is used. A film thickness measuring device using a halogen lamp or a spectrometer is used as a light source of this film thickness device, but there is a problem that it is expensive. In order to solve this problem, a film thickness measuring device using an LED as a light source as shown in FIG. 8 has been proposed (see Japanese Patent Laid-Open No. 2000-46525).

In this device, light emitted from a light emitting diode (LED) which is the light source 1 emits light from an optical fiber 3 on the light projecting side.
After passing through, the light emitting unit 4 irradiates the wafer which is the sample 5 with the light. The reflected light from the sample 5 is guided again by the light emitting unit 4 and the light receiving side optical fiber 6 and reaches the light detecting unit 8. The photodetector 8 measures the intensity of the incident light and sends the signal to the calculator 9 to perform necessary calculations to measure the film thickness.

However, in this device, in the LED 1, since the light emitting element on the chip in the package emits light, the chip and the bonding are projected as an image. Therefore, the light emission intensity distribution of the LED 1 has large unevenness. In addition, the light emitting side optical fiber 3 and the light receiving side optical fiber 6
There is a large variation in the arrangement of the optical fiber bundles.
Therefore, the light amount distribution of the light emitted from the light projecting side optical fiber 3 and the light emitting portion 4 to the wafer 5 is not uniform, and further, the reflected light from the wafer 5 guided to the light detecting portion 8 is also not uniform. The accuracy of strength measurement may deteriorate.

Also, due to mechanical tolerances of the components,
When vignetting occurs on the optical axis, there is a problem in that the amount of light applied to the light projecting side optical fiber 3 and the amount of light guided to the light detection unit 8 are greatly impaired.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly accurate film thickness measuring device. According to the present invention, the light amount distribution of the light irradiating the sample and the light incident on the photodetector is made uniform by each of the following means, and further, L
It is possible to eliminate the influence of vignetting on the optical axes of the ED-light projecting side optical fiber and the light receiving side optical fiber-photodetector.

[0007]

The present invention has taken the following means in order to solve the above problems.

A light intensity measuring apparatus according to a first aspect of the present invention includes a light source, a first condensing optical system for condensing light from the light source onto a sample, and condensing reflected light from the sample. A second condensing optical system, a photodetector that detects reflected light from the sample through the second condensing optical system, and a change in the light intensity of the reflected light detected by the photodetector. Means for arranging any one of the samples at a defocus position of the first condensing optical system, and a light receiving surface of the photodetection unit for defocusing the second condensing optical system. It is characterized in that at least one of the means for arranging the position is provided.

A light intensity measuring device according to a second aspect of the present invention is for irradiating a light source, a condensing optical system for condensing light from the light source, and light from the condensing optical system onto a sample. Light emitting means, a light detecting section for detecting the reflected light from the sample, and a measuring means for measuring the change in the light intensity of the reflected light detected by the light detecting section, the incident end of the light emitting means, It is characterized in that it is arranged at a defocus position of the condensing optical system.

A light intensity measuring apparatus according to a third aspect of the present invention is a light source for illuminating a sample, a condensing optical system for condensing reflected light from the sample, and the sample through the condensing optical system. In a light intensity measuring device comprising a light detecting section for detecting reflected light from the light detecting section and a measuring means for measuring the light intensity change of the reflected light detected by the light detecting section, the light source and the light receiving surface of the light detecting section. At least one of them is arranged at the defocus position of the condensing optical system.

A preferred embodiment of the above-mentioned light intensity measuring device is as follows. The following embodiments may be applied individually or in appropriate combination. (1) At least a part of the light emitting means is composed of an optical fiber. (2) The irradiation area of the defocused light from the first condensing optical system is larger than the effective area of the incident end of the light emitting means. (3) The irradiation area of the defocused light from the condensing optical system is larger than the effective light receiving area of the light receiving surface of the photodetector. (4) At least one light emitting diode is used as the light source.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is a view showing a schematic structure of a film thickness measuring apparatus according to a first embodiment of the present invention, and the entire structure is shown in FIG. The film thickness measuring device shown in FIG. 1 is a film thickness measuring device for measuring the film thickness formed on a semiconductor wafer or the like. In each of the following embodiments, a film thickness measuring device will be described as an example, but the present invention is not limited to this, and the present invention is applicable to a device for measuring light intensity, for example, completion of film formation or etching of a semiconductor substrate or the like. It can also be applied to inspection devices and real-time film thickness monitors.

In FIG. 1, an LED light source 1 emits light for irradiating a sample. The light emitted from the LED light source 1 is transmitted through the light-projecting-side condenser lens 2 to the light-projecting-side optical fiber 3
Incident on the introduction part of. A partially enlarged view of the LED light source 1, the light-projecting-side condenser lens 2, and the light-projecting-side optical fiber 3 is shown in FIG. As shown in FIG. 1B, in the present embodiment, the introduction portion of the light projecting side optical fiber 3 is arranged at a position different from the focal length f1 of the light projecting side condenser lens 2 (hereinafter The arrangement at a position different from the focal length is referred to as "defocus" in this specification). That is,
The light emitted from the LED light source 1 is not focused on the image 11 at the position of the focal length f1, but is defocused by the light-projecting-side condenser lens 2 to the introduction portion of the light-projecting-side optical fiber 3 and is condensed. The emitted light is condensed in a wider range than the introduction part of the light projecting side optical fiber 3. Therefore, as for the image of the LED chip 10, the defocused image 12 is collected at the position of the introduction portion of the light projecting side optical fiber 3. Figure 1
This is shown in (c). 1C is a view taken along the line 1C-1C in FIG. As shown in (c) of FIG. 1, the image 12 defocused at the position of the introduction portion of the light projecting side optical fiber 3 is condensed so as to be larger than the area of the fiber bundle 13.

The light incident on the introduction part of the light projecting side optical fiber 3 is a light emitting part 4 arranged at the other end of the light projecting side optical fiber 3.
The sample 5 is irradiated via. This sample 5 is a semiconductor substrate or a glass substrate for a liquid crystal panel,
It is fixed to a stage (not shown) that can be driven in three axis directions. Then, the reflected light from the sample 5 passes through the light emitting portion 4 and the light receiving side optical fiber 6 again, and the light receiving side condensing lens 7
Is incident on the light receiving surface of the photodetector 8. Light detector 8
Measures the intensity of the incident light and sends a signal relating to the measurement result to the arithmetic unit 9. The calculation unit 9 performs a necessary calculation based on the signal sent from the light detection unit 8. The photodetector 8 may be of any type as long as it can measure the light intensity. For example, a spectroscope, a photomultiplier tube, a photodiode, or the like is used. In addition, necessary calculation is performed in the calculation unit 9, the film pressure of the sample 5 is measured, and an external device (not shown) is controlled as necessary.

The present embodiment is characterized in that the incident light at the introduction portion of the light projecting side optical fiber 3 is defocused. The operation of this embodiment will be described with reference to FIG. FIG. 2 is a graph showing the relationship between the center distance between the image condensed at the focal position and the defocused image, and the light amount,
(A) is an image condensed at the focal position, and (b) is a defocused image. As shown in (a) of FIG.
The image condensed at the focal position accurately reflects the intensity distribution from the LED light source 1, and a sharp image is obtained. On the other hand, as shown in FIG. 2B, the defocused image has a more uniform light amount distribution than the image focused at the focal position. The image 12 defocused at the position where the light-projecting side optical fiber 3 is introduced is focused so as to be larger than the area of the fiber bundle 13.

As described above, according to the present embodiment, by defocusing the light focused on the light projecting side optical fiber 3, the light amount distribution of the light irradiating the sample 5 becomes uniform, so that the film thickness The influence of measurement accuracy deterioration is reduced. Further, by converging the image 12 of the LED light source 1 so as to be large on the fiber bundle 13 of the light projecting side optical fibers, L
The influence of light amount attenuation due to vignetting with respect to the optical axis due to mechanical tolerances of components that fix the ED light source 1 and the projection side optical fiber 3 is reduced. Therefore, according to this embodiment, highly accurate film thickness measurement can be performed.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows the second aspect of the present invention.
FIG. 4 is a diagram showing a schematic configuration of a film thickness measuring device according to the embodiment of the present invention, wherein (a) is a diagram showing an overall configuration, and (b) is a light-receiving side optical fiber 6, a light-receiving side condensing lens 7, and light detection It is an enlarged view of the part 8, (c) is a 3C-3C arrow view of (b). In FIG. 3, the same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the introduction part of the light projecting side optical fiber 3 is arranged at the focal position f1 of the light projecting side condensing lens 2. Then, as shown in FIG. 3B, the photodetector 8 is arranged at a position (that is, a defocus position) different from the focal position f2 of the light-receiving side condenser lens 7. Further, as shown in FIG. 3C, the light-receiving side condensing lens 7 is configured so that the image 14 from the light-receiving side optical fiber 6 is condensed so as to be larger than the area of the light-receiving surface 15 of the photodetector 8. is doing. As a result, the light incident on the light receiving surface of the light detecting unit 8 has a more uniform light amount distribution than when the light detecting unit 8 is at the focal position f2 of the light receiving side condenser lens 7, and the light detecting unit 8 Is incident on the light receiving surface of. The reason for this is the same as in the first embodiment.

As described above, the first embodiment also
Similar to the embodiment described above, by defocusing the incident light on the photodetector 8 to make it uniform, the influence of the deterioration of the film thickness measurement accuracy due to the unevenness of the LED light source 1 is reduced. Further, by condensing the image 14 of the light-receiving side optical fiber 6 so as to be larger than the area of the light-receiving surface 15 of the light detecting section 8, the machine of the component fixing the light detecting section 8-the light receiving side optical fiber 6. The influence of light amount attenuation due to vignetting on the optical axis due to tolerance and the like is reduced.

(Third Embodiment) A third embodiment of the present invention will be described with reference to FIG. FIG. 4 shows the third aspect of the present invention.
It is a figure which shows schematic structure of the film thickness measuring apparatus which concerns on embodiment of this. In FIG. 4, the same parts as those in FIGS. 1 and 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the light projecting side optical fiber 3 is obtained by combining the first embodiment and the second embodiment.
Is arranged at a position different from the focal length f1 of the light projecting side condenser lens 2, and the light detecting part 8 is arranged at a position different from the focus position f2 of the light receiving side condenser lens 7. Specifically, it is as follows.

The light emitted from the LED light source 1 is focused on the light projecting side optical fiber 3 by the light projecting side collecting lens 2 from the right side of FIG. As shown in FIG. 1B, the image of the LED chip 10 is an image 11 condensed at the position of the focal length f1.
Instead, the defocused image 12 is collected at the position of the introduction part of the light projecting side optical fiber 3. Therefore, the sample 5 is irradiated with light having a uniform light amount distribution from the light emitting unit 4. Further, the reflected light from the sample 5 is again introduced into the light receiving side optical fiber 6 via the light emitting portion 4, and the light from the other end of the light receiving side optical fiber 6 is received as shown in FIG. 3B. The side condenser lens 7 defocuses and detects the light on the photodetector 8. Therefore, the light incident on the photodetector 8 has a more uniform light amount distribution than when the photodetector 8 is arranged at the distance of the focus position f2 from the light-receiving side condenser lens 7.

In this embodiment, the sample 5 is defocused by defocusing the light introduced into the light projecting side optical fiber 3.
Since the light amount distribution of the light irradiating the laser light is uniform and the incident light to the photodetector 8 is defocused to be uniform light, the influence of the deterioration of the accuracy of the film thickness measurement on the photodetector is further reduced. To be done.

(Fourth Embodiment) A fourth embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a fourth embodiment of the present invention.
It is a figure which shows schematic structure of the film thickness measuring apparatus which concerns on embodiment of this. 5, the same parts as those in FIG. 4 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, a plurality of LED light sources are used in the third embodiment. That is, the film thickness measuring device according to the present embodiment includes a plurality of LED light sources 1a,
1b, light projecting side condenser lenses 2a, 2b, light projecting side fiber 1
4, a light emitting part 4, a sample 5, a light receiving side optical fiber 6, a light receiving side condensing lens 7, and a light detecting part 8. In this configuration, the introduction part of the light projecting side optical fiber 20 is arranged at a position different from the focal lengths f1a and f1b of the light projecting side condensing lenses 2a, 2b, and the light detecting part 8 is arranged on the light receiving side condensing lens. It is arranged at a position different from the focal position f2 of No. 7.

Specifically, the light emitted from the LED light sources 1a and 1b is introduced into the light projecting side optical fiber 20 by the light projecting side condenser lenses 2a and 2b. Here, as in the third embodiment, the defocused image 12 is collected at the introduction position of the light-receiving side optical fiber 6. Then, the defocused image is introduced into the light emitting unit 4 from the other end of the light projecting side optical fiber 20, and in the light emitting unit 4, the plurality of light sources 1a, 1b.
The lights from the above are added together and the sample 5 is irradiated. Sample 5
The light reflected from is defocused and detected by the photodetector 8 as in the third embodiment.

According to this embodiment, in addition to the effects of the first embodiment, by using a plurality of monochromatic LEDs,
It is possible to irradiate the sample 5 with stronger and uniform light.

In the present embodiment, the light sources 1a, 1
b can also be turned on independently. Also, a plurality of L
The ED light sources 1a and 1b are not limited to having a plurality of the same colors, but may be LEDs of different colors, or a combination of an LED and a lamp, a halogen lamp and a Xe lamp. In this way, by using the light sources of a plurality of colors, it becomes possible to select the light source color according to the sample.

(Fifth Embodiment) A fifth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a diagram showing an embodiment in which a slide mechanism capable of adjusting the condenser lens on the light projecting side in the focus direction (that is, the optical axis direction) is provided. In FIG. 6, the same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 6, in this embodiment, a slide mechanism (not shown) capable of moving the condenser lens 2 is provided to make the focal position variable.
With such a configuration, the condenser lens 2 is moved in the focus direction (arrow direction in the drawing) and the focus position is adjusted, so that the image of the LED chip 10 is adjusted to an optimum state. , The light emitted from the LED light source 1 is condensed on the introduction part of the light projecting side optical fiber 3.

As described above, the position of the condenser lens 2 can be moved so that the focal position can be adjusted arbitrarily, mechanical tolerances of the LED light source 1, the peripheral parts of the optical fiber 3 on the light projecting side, and the like. The user can set the optimum position even if there are variations due to assembly or the like.

In this embodiment, only the light projecting side condenser lens 2 is movable, but the invention is not limited to this.
For example, the LED light source 1 and the light projecting side optical fiber 3 may be movable. Further, the LED light source 1, the light-projecting-side condenser lens 2, and the light-projecting-side optical fiber 3 may all move simultaneously.

(Sixth Embodiment) A sixth embodiment of the present invention will be described with reference to FIG. FIG. 7 shows a sixth embodiment of the present invention.
It is a figure which shows schematic structure of the film thickness measuring apparatus which concerns on embodiment of this. In FIG. 7, the same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. In the present embodiment, unlike the first to fourth embodiments, the optical path of the light projecting portion and the light receiving portion is split by the half mirror 21 without using an optical fiber, and the focus position f13 of the condenser lens 22 is changed. The LED light source 1 and the light detection unit 8 are installed at different positions (that is, defocus positions).

In the present embodiment, as shown in FIG. 7, the light emitted from the LED light source 1 is emitted from the half mirror 2
1 and is introduced into the condenser lens 22. LE at this time
Since the D light source 1 is arranged at a position different from the focal length f3 of the condenser lens 22, the image of the LED light source 1 is defocused and condensed on the sample 5. The reflected light from the sample 5 is deflected from the condenser lens 22 by the half mirror 21, defocused, and condensed on the photodetector 8.

Also in this embodiment, the same effect as that of the first embodiment can be obtained and the number of constituent parts can be reduced as compared with the first embodiment.

In the present embodiment, an example in which both the LED light source 1 and the light detecting section 8 are defocused has been shown, but only one of them may be used.

The present invention is not limited to the above embodiments of the invention. In each of the above-described embodiments, the embodiment applied to the film thickness measuring device has been described, but the present invention is not limited to this, and a semiconductor, a liquid crystal panel manufacturing film forming, etching, a flattening process end point detecting device, a real-time film. The present invention can be applied to a light intensity measuring device such as a thickness monitor. Further, the LED light source 1 is an LE in which a single color, white color, and a plurality of color chips are packaged in one package.
One package LED such as D, and further, not limited to the LED, a halogen lamp or a Xe lamp can be used as a light source. In the above embodiment, L
Needless to say, various modifications can be made without departing from the scope of the present invention, such as ED.

[0038]

According to the present invention, even if a light source having a large unevenness of the light quantity distribution is used, the light quantity distribution of the light irradiating the sample becomes uniform, and the influence of the deterioration of the accuracy of the film thickness measurement is reduced. in addition,
The influence of light amount attenuation due to vignetting or the like with respect to the optical axis, which is caused by mechanical tolerance of each component on the light projecting side, is reduced.
Therefore, the accuracy of measurement is improved.

Further, by applying the LED to the light source, the space saving of the device and the maintainability are improved. Furthermore,
By using the optical fiber, the degree of freedom in installing the device space is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a film thickness measuring device according to a first embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the center distance between a focused image and a defocused image at the focal position and the amount of light.

FIG. 3 is a diagram showing a schematic configuration of a film thickness measuring device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a schematic configuration of a film thickness measuring device according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a schematic configuration of a film thickness measuring device according to a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a schematic configuration of a film thickness measuring device according to a fifth embodiment of the present invention.

FIG. 7 is a diagram showing a schematic configuration of a film thickness measuring device according to a sixth embodiment of the present invention.

FIG. 8 is a diagram for explaining a conventional example.

[Explanation of symbols]

1, 1a, 1b ... Light source (LED light source) 2, 2a, 2b ... Condensing lens on projection side 3 ... Emitter side optical fiber 4 ... Light emitting part 5 ... Sample (wafer) 6 ... Receiving side optical fiber 7 ... Receiving side condenser lens 8 ... Photodetector 9 ... Operation unit 10 ... LED chip 11 ... Statue 12 ... Statue 13 ... Fiber bundle 14 ... Emitter side fiber 15 ... Light receiving surface 20 ... Emitter side optical fiber 21 ... Half mirror 22 ... Condensing lens

Continued front page    F term (reference) 2F065 AA30 AA55 BB13 BB17 CC17                       DD03 FF44 LL02 NN01 PP12                       QQ26 UU01                 2H088 FA11 FA30 MA20                 4M106 AA01 BA10 CA48 DH03 DH12                       DH31 DH38 DH40 DJ20

Claims (6)

[Claims] 1. A light source, a first condensing optical system that condenses light from the light source onto a sample, a second condensing optical system that condenses reflected light from the sample, and the first condensing optical system. A light detection unit for detecting reflected light from the sample through the light collecting optical system 2;
In a light intensity measuring device including a measuring unit that measures a light intensity change of reflected light detected by the light detecting unit, a unit that arranges the sample at a defocus position of the first condensing optical system, and A light intensity measuring apparatus comprising at least one of means for arranging a light receiving surface of a light detecting portion at a defocus position of the second condensing optical system. 2. A light source, a condensing optical system for condensing the light from the light source, a light emitting means for irradiating the sample with the light from the condensing optical system, and a reflected light from the sample. In a light intensity measuring device comprising a light detecting unit for detecting and a measuring unit for measuring the light intensity change of the reflected light detected by the light detecting unit, the incident end of the light emitting unit is set to the condensing optical system. A light intensity measuring device, which is arranged at a defocus position. 3. The light intensity measuring device according to claim 2, wherein at least a part of the light emitting means is composed of an optical fiber. 4. The light intensity measuring device according to claim 2, wherein the irradiation area of the defocused light from the first condensing optical system is the incident end of the light emitting means. The light intensity measuring device is characterized by being larger than the effective area of. 5. A light source that illuminates a sample, a condensing optical system that condenses reflected light from the sample, and a photodetector that detects reflected light from the sample through the condensing optical system, In a light intensity measuring device including a measuring unit that measures a change in the light intensity of the reflected light detected by the light detecting unit, at least one of the light source and the light receiving surface of the light detecting unit is connected to the defocusing optical system. A light intensity measuring device, which is arranged at a focus position. 6. The light intensity measuring device according to claim 1, wherein an irradiation area of the defocused light from the condensing optical system is an effective area of a light receiving surface of the light detecting section. A light intensity measuring device characterized by being larger than a light receiving area.